The present invention relates to a technique for permitting construction or implementation, at low cost, of an apparatus which can use a plurality of tone generator devices with no function to share a same waveform memory, to perform processing similar to that performed by a plurality of tone generator devices with a function to share a same waveform memory.
Heretofore, tone generator apparatus have been known, which use two tone generators (e.g., in the form of tone generator chips) to increase the number of tone generation channels (CHs) and store, in a single waveform (data) memory, all waveform data to be used for generation of tones, and in which each of the two tone generators can read out waveform data from the waveform memory. In Japanese patent Application Laid-open Publication No. HEI-9-146551, for example, there is disclosed a waveform-memory-based tone generator apparatus, in which a single waveform memory is shared between two tone generators and in which the tone generators can each access the same waveform memory on a time-divisional basis to thereby read out waveform data from the memory substantially simultaneously; that is, the disclosed tone generator apparatus has a waveform memory sharing function. With the disclosed technique, any newly-generated tone generation instruction can be allotted to any of the channels of the two tone generators.
In the tone generator apparatus disclosed in the No. HEI-9-146551, the two tone generators each have to have a function for sharing the waveform memory (i.e., waveform-memory sharing function). Generally, the tone generator having a waveform-memory sharing function and the tone generator having no waveform-memory sharing function significantly differ in price; namely, the tone generator with the waveform-memory sharing function is more expensive than the tone generator without the waveform-memory sharing function. Whereas the tone generator without the waveform-memory sharing function is inexpensive, it can use only a dedicated waveform memory. Thus, as the number of tone generators is increased to increase the number of channels, there also arises a need to increase the number of waveform memories for storing waveform data. Particularly, in order to allow sets of waveform data, representative of all tone colors used in the apparatus, to be shared between two tone generators, it is necessary to prestore all of such necessary sets of waveform data redundantly in both of the waveform memories of the two tone generators. Providing two waveform memories storing all necessary sets of waveform data as mentioned above would result in increased memory cost.